Several derivatives of indane-diones and 4-hydroxycoumarins are known to possess the property of lowering the amount of prothrombin in the blood. For this reason, they may be used as rodenticides, producing high mortality in rats and mice by causing internal hemorrhaging. However, compositions containing these compounds lack satisfactory storage properties, tending to be unstable or tending to render bait to which they are applied unattractive to rodents.
U.S. Pat. No. 3,867,546, teaches that certain such rodenticides have an adequate degree of solubility in polyoxyethylene glycols to permit the preparation of solutions which are stable in time. This method, however, cannot be extended to certain other rodenticides of this class or to other glycols because of the problem of limited solubility. In order to obtain the advantages of a stable solution, a sufficient concentration must be achieved.